Pyspark: Replacing value in a column by searching

问题:

I'm a newbie in PySpark.

I have a Spark DataFrame df that has a column 'device_type'.

I want to replace every value that is in "Tablet" or "Phone" to "Phone", and replace "PC" to "Desktop".

In Python I can do the following,

deviceDict = {'Tablet':'Mobile','Phone':'Mobile','PC':'Desktop'}
df['device_type'] = df['device_type'].replace(deviceDict,inplace=False)

How can I achieve this using PySpark? Thanks!

回答1:

You can use either na.replace:

df = spark.createDataFrame([
    ('Tablet', ), ('Phone', ),  ('PC', ), ('Other', ), (None, )
], ["device_type"])

df.na.replace(deviceDict, 1).show()

+-----------+
|device_type|
+-----------+
|     Mobile|
|     Mobile|
|    Desktop|
|      Other|
|       null|
+-----------+

or map literal:

from itertools import chain
from pyspark.sql.functions import create_map, lit

mapping = create_map([lit(x) for x in chain(*deviceDict.items())])


df.select(mapping[df['device_type']].alias('device_type'))

+-----------+
|device_type|
+-----------+
|     Mobile|
|     Mobile|
|    Desktop|
|       null|
|       null|
+-----------+

Please note that the latter solution will convert values not present in the mapping to NULL. If this is not a desired behavior you can add coalesce:

from pyspark.sql.functions import coalesce


df.select(
    coalesce(mapping[df['device_type']], df['device_type']).alias('device_type')
)

+-----------+
|device_type|
+-----------+
|     Mobile|
|     Mobile|
|    Desktop|
|      Other|
|       null|
+-----------+

回答2:

You can do this using df.withColumn too:

from itertools import chain
from pyspark.sql.functions import create_map, lit

deviceDict = {'Tablet':'Mobile','Phone':'Mobile','PC':'Desktop'}

mapping_expr = create_map([lit(x) for x in chain(*deviceDict.items())])

df = df.withColumn('device_type', mapping_expr[df['dvice_type']])
df.show()